Medical device and locking mechanism therefor

ABSTRACT

A locking mechanism  10  for a medical sharp device such as a syringe assembly  62  includes a retainer part  12  for retaining a hypodermic needle  22 , and a connector part  14 . The retainer part includes lugs  46  for engagement with a recess  82  formed in a neck  70  of the syringe assembly. When a plunger  72  of the syringe assembly is pushed fully forwards, the lugs  56  of the retainer part  12  engage behind a ledge  54  of the connector part  14  and the lugs  46  disengage from the recess  82 . The plunger  72  may then be retracted, pulling the needle  22  into the barrel  64  of the assembly. The neck portion may be eccentrically mounted on the barrel and means  116,118  may be provided for preventing rotation of the plunger  72  in the barrel  64.

The present invention relates to locking mechanisms for controllingengagement between parts moveable relative to one another in medicalsharp devices. The invention also relates to medical devices, such ashypodermic needle devices including syringe assemblies, cannulas andcatheters including butterfly catheters, which incorporate suchmechanisms. The invention also relates to hypodermic needle assemblies.

There is a need for non-reusable safe medical sharp devices such ashypodermic syringes. It is known that the reuse of hypodermic needledevices is unsafe practice. There is a risk to patients and others ofinfection. The improper disposal of used syringes and needles alsopresents a risk to healthcare workers and others. It is also known thatneedlestick incidents are undesirable for both healthcare workers andpatients since infections such as HIV, Hepatitis B and C, Ebola fever,Lassa fever, Syphilis, Tuberculosis, Herpes, Brucellosis andStreptococcal conditions may be accidentally transmitted duringneedlestick incidents.

Furthermore, it is now believed that the BSE and/or vCJD protein orproteins may be resistant to sterilisation processes such that theproblems and dangers of reuse of human medicine sharp devices are alsoapplicable in veterinary medicine.

Some attempts have been made to address the above problems by providingwhat are known as “safety” syringes which are supposed to be non-usableonce they have been used once. One type of known “safety” syringeincludes a spring which is adapted to force a hypodermic needlebackwards into a retracted position inside a barrel of a hypodermicsyringe. A problem with this type of apparatus is that the spring cancause the hypodermic needle to spring back suddenly out of the patient,causing discomfort to the patient especially when the operator of thedevice is applying a slight bending moment to the needle at the time ofthe sudden needle retraction by the spring. Furthermore, the spring canbe very expensive, since the steel used can be required by medicalstandards to remain sterile for a number of years and thus veryexpensive steel must be employed.

Another type of known “safety” syringe include an outer barrel which issprung forwards by a spring along the main syringe barrel and over theneedle once a plunger of the syringe has been depressed. The mechanismis very complicated and expensive due to the need for the spring andadditional sheath barrel.

Another type of known “safety” syringe, as described in U.S. Pat. No.5,431,631, includes a mushroom-shaped locking device for locking thefront of a hypodermic needle assembly's plunger to a needle retaineronce the plunger has been fully depressed. The plunger may then bemanually retracted, overcoming the rather complicated engagement at aforward location between a bead on the retainer part and the barrel.This arrangement is not only complicated and expensive incorporating anumber of parts, but the patient may feel an uncomfortable sensation asthe mushroom-shaped part suddenly engages. Furthermore, the needle isspaced a substantial distance in front of the end of plunger movementalong the barrel meaning that, when the device is used for injectionpurposes, substantial volume of the material to be injected is wasted.

Known types of “safety” syringe are very expensive being up to ten timesmore costly than “standard” syringes of the reusable type. Although theuse of reusable syringes is mandatory in some jurisdictions, the cost ofknown “safety” syringes is such that it is proving difficult to complywith this mandatory requirement.

Known hypodermic needle assemblies use glue to retain and seal the steelneedle of the assembly in a retainer part therefor. The use of glue issomewhat unreliable and has a cost implication.

Furthermore, in known systems it is often not possible to change needlesbefore use of an assembly. In cases in which this is possible, there isoften a substantial non-displaced volume of fluid in front of a plungerof the device when the plunger is fully depressed and this means that asubstantial amount of fluid is wasted when using the device forinjection purposes.

The present invention aims to alleviate at least some of the problems ofthe prior art.

According to a first aspect of the present invention there is provided alocking mechanism as set out in claim 1. This locking mechanism ishighly advantageous since it is very simple and can be incorporated in acost-effective manner into various types of medical device, such ashypodermic syringes for injection or extraction of material frompatients in a cost-effective manner. Furthermore, in preferredembodiments of the invention, the locking mechanism can be incorporatedto allow one actuation of the device, followed by retraction of themedical sharp device. The medical sharp device will normally comprise aneedle, but may comprise other types of sharp device, such as a knife orother cutting instrument.

A number of preferred features of the locking mechanism will now bedescribed.

The first formation may comprise a lug and the second formation maycomprise a recess or cavity formed in the body. A pair of said lugs maybe provided on opposite sides of the retainer part and the recess maycomprise an annular recess in the body part.

Preferably, the retainer part includes a flexible leg, the firstformation being located on the leg, the connector part being adapted toflex the leg on engagement with the retainer part to move the firstformation relative to the body part. Most preferably, the said retainerpart includes at least two said legs, the connector part being adaptedto move the said legs towards one another on engagement with theretainer part. Therefore, before engagement of the retainer part by theconnector part, the legs may be outwardly biased for engagement with thebody part for holding the retainer part firmly relative to the bodypart, but on engagement of the retainer part by the connector part, theconnector part may move the said legs for reducing the effectiveness ofengagement between the retainer part and the body part, and theconnector part may then be moved for disengaging the retainer part fromthe body part.

The connector part may be linearly moveable to engage the retainer part,the connector part, on engagement with the retainer part, causingmovement of at least one said leg in a direction generally perpendicularto the said direction of movement of the connector part.

The said legs may be mutually joined at respective ends thereof.Preferably, the legs form a diamond shape when their respective ends arejoined. Accordingly, the structure formed by the legs may be relativelyresilient, such that, when the legs are engaged with the body part, theengagement is relatively effective.

The body part may take various forms but will usually be an item fixedto or part of a main body of the medical device. Thus the body part maycomprise, for example, a central tubular body part of a catheter e.g. abutterfly catheter or cannula, or may comprise a portion of a barrelpart of a hypodermic needle assembly, such as a neck portion of such anassembly, especially when the barrel comprises a main cylindrical partjoined at a front end thereof by a tapered or conical shoulder to aneck.

The body part may comprise an element releasably coupled to a main bodyof a medical device, for example, a releasable needle retention hub inthe case of a hypodermic needle assembly.

Preferably, each said leg has an inner surface and an outer surface, theouter surface being longer than the inner surface. It is believed thatthis construction has the advantage that the leg will be relativelyresilient against bending in response to engagement thereof by theconnector part. The inner surface of the leg may be relatively flat andthe outer surface may be curved or outwardly convex, in order to providethe longer configuration of the outer surface relative to the innersurface.

The connector part preferably comprises a generally cylindrical element.The connector part may include an internal bore into which at least partof the retainer part is insertable. The connector part preferablyincludes an annular ledge at an entrance to the bore. The retainer partpreferably includes at least one connector protrusion for engagementbehind the annular ledge. Preferably, two said connector protrusions areprovided, the connector protrusions being asymmetrically configured forasymmetrically configured for asymmetrically engaging the annular ledge.Thus, the engagement between the connector protrusions and the annularledge may be such that the connector part provides a tilting force onthe retainer part, and this may be highly beneficial when the retainerpart is used to retain a hypodermic needle, so that in preferredembodiments the needle may be retracted inside a barrel of a hypodermicsyringe and then automatically tilted by the locking mechanism, e.g. sothat it cannot be reused.

In a preferred embodiment, the retainer part is adapted to retain ahypodermic needle, the retainer part including an elongate bore passingtherethrough, the bore being engageable with a cylindrical outer surfaceof a needle. Preferably, the elongate bore includes internal ribs, suchas circumferentially extending ribs, for sealingly gripping a needle,for example, with a push-fit and/or interference fit. Accordingly, it isnot necessary to use glue to mount the needle.

Accordingly, according to a second aspect of the present invention thereis provided a hypodermic needle assembly as set out in claim 23. Thesubstantial advantage of a push fit sealing engagement between theneedle and the retainer for the needle is that glue is not needed. Thepush-fit may alternatively or additionally comprise an interference fit(e.g. a push interference fit or a shrink interference fit in which theretainer part is shrunk on to the needle. Therefore, the unreliabilityand cost of using glue may be avoided.

The bore preferably includes a series of ribs for sealingly engaging anouter surface of the needle. The ribs are preferably circumferentiallyextending ribs. This has the advantage that the needle is gripped at anumber of locations spaced axially therealong, and the series of ribsprovide a series of sealing engagements between the needle and retainersuch that the sealing between the needle and retainer is relativelyeffective.

A further aspect of the invention provides a hypodermic needle assemblyas set out in claim 26. Various optional features are mentioned inclaims 27 to 36.

A further aspect of the invention provides a medical device as set outin claim 37.

A further aspect of the invention provides a medical device as set outin claim 38. Preferably, the device comprises a hypodermic needledevice. The device may comprise a catheter (e.g. a butterfly catheter)or cannula or other hypodermic needle device. The medical device maycomprise a hypodermic syringe. In this case, the retainer part may beadapted to retain a hypodermic needle of the device and the connectorpart may be mounted on a plunger of the syringe. The hypodermic syringemay be used for injecting or extracting material such as fluid to orfrom a patient.

Preferably, the syringe includes a barrel, the barrel having a maincylindrical part, a conical or tapered shoulder portion at a forward endof the main cylindrical part, and a neck portion in front of theshoulder portion, the said second formation of the locking mechanismbeing formed internally in the neck portion of the barrel. Preferably,the neck portion of the barrel includes a front end and a rear endthereof, the rear end being adjacent a front end of the shoulderportion, the second formation of the locking mechanism comprising anannular internal recess or cavity formed at the rear end of the neckportion. It will therefore be appreciated that an advantage of thelocation of the second formation at the rear end of the neck portion isthat the hypodermic needle may be located at least partially inside theneck portion with the adjacent end of the hypodermic needle locatedinside the neck portion and preferably no more than 25% or 50% of theway along the neck portion from the rear end thereof, such that, whenused for injecting fluid, a small amount of fluid/material will bewasted.

Preferably, the device includes a hub part for releasably sealablyretaining the retainer part on the barrel of the syringe. Thus, theretainer part and needle may be removed from the device and replaced,such as with a retainer and needle of different configuration, such aswhen a different needle diameter or gauge is required. The hub mayinclude a stop surface for preventing forward movement of the retainerpart relative to the barrel. Thus, when the plunger is pushed forwards,the hub maintains the retainer part and needle in position, but once theconnector part has engaged the retainer part and altered the engagementbetween the retainer part and the body part, e.g. the preferred annularrecess in the neck portion of the barrel, the plunger may be retractedsuch that the connector part may pull the retainer part and needle intothe barrel. The plunger preferably includes a weak region, such thatafter use, the plunger may, if desired, be snapped to assist inpreventing further use of the device. Furthermore, the plungerpreferably includes a jam mechanism for preventing removal of the usedhypodermic needle from the barrel.

A further aspect of the invention provides a locking mechanism for amedical device comprising a retainer part for retaining medical sharpdevices, the retainer part including at least one connector portionthereof adapted for engagement against a body part of a medical sharpdevice, and a connector part, the connector part being adapted formovement to engage the connector portion for connection therewith,movement of the connector part once connected to the connector portioncausing movement of the retainer part.

Preferably, the connector portion comprising a flexible leg.

Preferably, two said flexible legs are provided extending generallyparallel to one another, engagement of the connector part with the legscausing the legs to move towards one another.

Preferably, the legs are joined together in a diamond shape preferablyhaving a general V-shaped end portion joined to an inwardly taperingportion adjacent a needle retaining body of the retainer.

Preferably, each said leg includes a lug adapted for engagement with arecess formed in the body part, the movement of the connector part toengage the leg causing a reduction in the force of engagement betweenthe lug and recess.

Preferably, the connector part includes a generally cylindrical bore,the bore being adapted to receive each said leg on engagement of theconnector part therewith.

Preferably, the bore includes an annular ledge at an entrance theretoand each said leg includes a connector projection adapted to ride overand lock past the ledge on insertion into the bore.

Another aspect of the invention is set out in claim 53. Various optionalfeatures are mentioned in claims 54 to 56.

The present invention may be carried out in various ways and a preferredembodiment of a locking mechanism and its incorporation in a preferredhypodermic syringe assembly and preferred butterfly catheter inaccordance with the invention will now be described by way of examplewith reference to the accompanying drawings, in which:

FIGS. 1A to 1C are various schematic side views of a preferredembodiment of a locking mechanism in accordance with the presentinvention, a preferred retainer part thereof retaining a hypodermicneedle;

FIG. 2 is a schematic sectional view in the direction 2 shown in FIG.1C;

FIG. 3 is a schematic sectional view in the direction 3 shown in FIG.1A;

FIGS. 4A to 4F are schematic side views showing the operation of thepreferred locking mechanism of FIGS. 1A to 1C and 2 and 4, incorporatedin a preferred hypodermic needle assembly;

FIG. 5 shows a schematic side view of an alternate hub for the assemblyof FIGS. 4A to 4F;

FIGS. 6A to 6D show various schematic side views of the lockingmechanism of FIGS. 1A to 1C when incorporated in a preferred butterflycatheter having a slightly shorter needle than the needle shown in FIGS.1A to 1C;

FIG. 7 is an enlarged side view of the retainer part and connector partshown in FIGS. 1 to 4;

FIG. 8 is a view corresponding to FIG. 7, in the direction of the arrowmarked 8 in FIG. 7;

FIG. 9 is a view corresponding to FIG. 8, in the direction “9” in FIG. 8but excluding the connector part 14;

FIG. 10 is an end view of an embodiment of a syringe assembly having aneccentrically located neck portion;

FIG. 11 is a further embodiment of a hypodermic needle assembly, inwhich the section of a barrel of the assembly is non-circular; and

FIG. 12 is a schematic side view of each of the assemblies shown inFIGS. 10 and 11.

A preferred locking mechanism 10 in accordance with a preferredembodiment of the present invention is shown in FIGS. 1A to 1C, FIG. 2and FIG. 3. The locking mechanism 10 comprises a retainer part 12 and aconnector part 14. The retainer part 12 includes a body part 16 or agenerally cylindrical needle retainer 16 having an elongate bore 18formed therethrough. An adjacent end 20 of a hypodermic needle 22 has acircular entrance aperture 24 thereto flush with one end 26 of the bore18. The other, distal end 28 of the needle 22 is sharp, and it will beunderstood that the needle 22 has an internal bore (or lumen) (notshown) formed therealong for the transmission of material, such asmedicine being injected to, or blood or other bodily fluids beingextracted from a patient.

The retainer part 12 includes a pair of resilient legs 30 formedintegrally with the cylindrical needle retainer 16, the legs 30 beingmutually joined at one end 32 thereof. The legs 32 form a diamond-shapedsection, consisting of V-shape end portion 31 adjacent an inwardlytapered portion 33 adjacent the needle retainer 16. The joining of thelegs in a “V” provides additional resilience against squashing thereofby the connector part 14 as will be described below. Furthermore, eachleg 30 includes a generally flat inner surface 34, formed by two flatsurfaces 36,38 and a generally concave or curved outer surface 40,formed by two surfaces 42,44. The arrangement of flat 34,36,38 surfacesand concave/curved 40,42,44 surfaces, provides additional resilience forthe legs 30 against movement towards one another.

FIGS. 7 to 9 show enlarged views of the retainer 12 and connector 14. Itwill be appreciated that the connector 14 is cylindrical and FIGS. 7 and8 thus show a schematic section through this part.

As shown in FIG. 3, each leg 30 includes a formation 46 formed thereonin the form of a lug 46 extending generally transverse to thelongitudinal direction of the needle 22.

As shown in FIGS. 4B and 7 to 9 the retainer 12 may include an annularseal 51 formed adjacent a rear end thereof (omitted for clarity in otherdrawings) for sealing inside the neck of the syringe. This seal islocated well inside the neck portion as is the rear entrance to theneedle and this means that almost no fluid is wasted as excess wheninjecting.

The seal 51 may be replaced with alternative sealing means in otherembodiments

The connector part 14 of the locking mechanism comprises a cup-shapedelement 48 having one end 50 which may be closed (or in otherembodiments open) and a second end 52 which is open but includes anannular ledge 54 which is inwardly extending at an entrance to the cup.The legs 30, in addition to the lugs 46 (which are symmetrically locatedabout the longitudinal axis of the hypodermic needle), includes twofurther lugs 56 which are located somewhat asymmetrically about the axisof the needle 22. The further lugs 56 are spaced further along the legs30 from the needle retainer part 16 of the retainer part 12 than thelugs 46.

As shown in the sequence of FIGS. 1A to 1C, the connector part 14 may bemoved linearly towards the retainer part 12 until the inner edge 58 ofthe ledge 54 engages the legs 30 as shown in FIG. 1B. Further movementof the connector part 14 linearly in the axial longitudinal direction ofthe needle 22 causes the legs 30 to be transversely moved towards oneanother. Eventually, the ledge 54 rides over the further lugs 56, thefurther lugs 56 having chamfered surfaces 58 allowing the ledge 54 toride over the lugs 56, but transverse flat surfaces 60 (perpendicular tothe needle axis) opposing the chamfered surfaces 58, the flat transversesurfaces 60 thus preventing removal of the connector part 14 from theretainer part 12, once the ledge 54 has ridden over the lugs 56 to placethe connector part 14 and retainer part 12 in the engaged configurationshown in FIG. 1C.

Thus, as shown in FIGS. 4A to 4F, the preferred locking mechanism 10 maybe incorporated in a preferred syringe assembly 62 in accordance with apreferred embodiment of the present invention.

As best shown in FIGS. 4A to 4F, the needle 22 is a push-fit in theneedle retainer 16, the needle retainer including a series ofcircumferential ribs on the internal bore 18 thereof, e.g. about tenspaced circumferentially extending ribs, the ribs 18 compressing againstthe needle 22 in order to hold the needle 22 in position and provide agood seal. Accordingly, it is not necessary to use glue to attach theneedle 22.

The syringe assembly 62 includes a barrel 64 having a main cylindricalpart 66, a conical shoulder 68 and a cylindrical neck 72. The assembly62 also has a plunger 72 having a stem 74 for operating a piston 76, thepiston 76 being sealed against the barrel main cylindrical part 66 withan O ring 78. The neck 70 of the barrel 64 includes at a rear end 80thereof an internal annular recess or cavity 82. The retainer part 12holding the needle 22 may be connected to a hub 84 (or the alternativehub 84 shown in FIG. 5) and, later, the retainer part 12 may be pushedinto the neck 70 of the barrel 64 to the configuration shown in FIG. 4Ain which the lugs 46 are resiliently engaged in the internal annularrecess 82 at the rear end 80 of the neck 70. The resilience of the lugs46 and the legs 30 is such that when the plunger 72 is drawn backwardsto draw material such as a vaccine, medicine or bodily material such asblood into the barrel 64, the retainer part 12 and hypodermic needle 22are retained in position, with transverse surfaces 61 of lugs 46engaging in the recess 82. Furthermore, the hub 84 is provided with astop element/stop surface 86 for preventing forward movement of theneedle 22 when the plunger 72 is pushed forwards. It will be appreciatedthat there is a gap 86 between the legs 30 such that fluid may flow fromthe barrel, through the gap 86 into the entrance aperture 24 and alongthe needle 22 or, of course, in the opposite direction.

When the syringe assembly 62 is used to give an injection, the plungeris pushed forwards, for example, from the position shown in FIG. 4A tothe position shown in FIG. 4B and then to the position shown in FIG. 4C.As the plunger 72 approaches the configuration shown in FIG. 4C, it willbe appreciated that the locking mechanism 10 adopts first theconfiguration shown in FIG. 1A, then the configuration shown in FIG. 1Band then the configuration shown in FIG. 1C which is the same as theconfiguration shown in FIG. 4C. As the connector part 14 of the lockingmechanism 10 moves along the legs 30, it squashes the legs 30 towardsone another and, in doing so, the lugs 46 disengage from the internalannular recess 82 in the neck portion 70 of the barrel 64 and, the ledge54 of the connector part 14 rides over the lugs 56. Accordingly, whenthe plunger 72 is pulled backwards to the position shown in FIG. 4B, theconnector part 14 pulls the retainer part 12 and needle 22 with it. Theneedle 22 maintains a generally longitudinally configuration until theend 28 passes through the neck portion 70 and along the inside of theshoulder 68 of the barrel. Due to the thin flat nature of the legs 30and the asymmetric configuration of the lugs 56, together with theinward squashing forces provided to the legs 30 by the ledge 54, theconnector part 14 provides a tilting force on the retainer part 12 andneedle 22, such that the needle tilts by about 5° as shown in FIG. 4Eand FIG. 4F, such that it is then not possible to push the needleforwards out through the neck 70 for reuse. Furthermore, the rear end 88of the barrel 64 includes a slight constriction 90 and the stem 74includes a jamming element 92 shown for the purposes of clarityschematically only and only in FIG. 4F, which prevents the stem 74 frombeing fully removed from the barrel 64. Thus, not only is the needle 22safely enclosed in the barrel 64 after use, but the needle 22 alsocannot be removed for attempted reuse on another apparatus. As indicatedin FIG. 4F, a weak spot 94 on the stem 74 of the plunger 72 convenientlyallows the plunger to be snapped for showing even the most inexperienceduser or persistent attempted reuser of needles 22 that the needle 22 hasbeen used and is now inoperative and should not be reused.

FIGS. 6A to 6D show a development on the apparatus shown in FIGS. 4A to4F in which the preferred locking mechanism 10 of FIGS. 1A to 1C, 2 and3 is instead incorporated in a butterfly catheter 100, this apparatusincluding a shorter needle 22. The locking mechanism 10 works on asimilar principle in FIGS. 6A to 6D and the connector part 14 has anopen end 102 which may be connected to a fluid tube 104 for variouspurposes such as provision of a drip (not shown). After use, the needle22 may be retracted into the butterfly device body 104 and a slightlyshorter needle retainer 16 of the retainer part 12 and the retainer 16shown in FIGS. 1 to 4 may be pulled longitudinally behind a tube section106 of the body 104 such that the needle retainer 16 cannot be pushedinside the tube 106 again and the needle 22 therefore cannot be pushedforwards out of the body 104 for reuse.

The embodiments of the invention, it is envisaged, may have applicationin the fields of both human and veterinary medicine.

It will be appreciated from the above that embodiments of the inventionmay provide a hypodermic medical device such as a syringe assembly inwhich a needle is secured, without glue or adhesive, in its optimalposition for use in injecting or extracting. The needle may besubsequently locked into the inner end of a plunger or piston to permitwithdrawal wholly into the barrel of the syringe or the body of thedevice. The complete assembly may then be discarded without fear ofaccidental infection through needlestick. The device/syringe is thusrendered safe and cannot be refilled or reused and it can be disposed ofsafely. The device may be produced in quantity at a competitive price.The retainer part 12 which may also be considered a central hub combinesa central channel for transmission of fluid being injected or extractedwith a ribbed internal contour that engages with the surface of theneedle. This internal locking mechanism shows that the needle is firmlysecured in a base that is in turn married with forward end or neck ofthe syringe barrel. The outer surface of the central hub or retainerpart is contoured such that the combined central hubs/retainer andneedle assembly can be easily and firmly attached to the neck of thesyringe barrel readying the syringe ready for use. The syringe may thenbe filled in the normal way for injection by drawing back the plunger,thus drawing injectable fluid into the barrel. The union of the needlehub and barrel of course forms an effective seal to prevent leakage andappropriate sealing means (not shown) are of course provided for thatpurpose. Once the injection is complete, and with the plunger fullydepressed, the piston engages the lugs 56 on the hubs that shut the hubtogether with the needle can be drawn back into the barrel of thesyringe. Due to the asymmetric nature of the lugs 56 and the resilienceof the legs and connector part, the needle tip 28 is displaced throughabout 5° as it is pulled back so that it is no longer in line with theaperture at the neck of the barrel and this prevents re-extension of theneedle and reuse of the syringe. With the needle fully withdrawn intothe barrel the whole assembly can be discarded. Subject to localprocedures, e.g. of a medical centre in which the device is used, it maybe permissible for the unit to be consigned to general waste rather thana sharps bin requiring special handling and disposal.

In the case of fluid extraction from the body, e.g. of blood, theplunger may be depressed to a point short of where the lugs 56 engagewith the connector part 12, and the plunger may then be retracted asfluid is drawn in. When the fluid is transferred into a vial (not shown)or other receptacle (not shown) the plunger will be fully depressed suchthat it engages with the lugs. Accordingly, when the plunger is pulledback again, the needle is withdrawn into the barrel of the syringe andthe unit can be discarded.

In devices such as catheters or butterflies which are in turn connectedto a drip or other equipment for the purpose of e.g. administeringfluids into the body, the locking of the needle is secured by pullingthe tail-end of the device until the needle disappears into the device.

Further advantages of preferred embodiments of the present inventionwill be apparent in that needles may be interchanged before use so thatthe clinician or other user can match a selection of needles with aselection of barrels. Thus, a standard barrel may be capable of taking arange of needle sizes and profiles, while larger or smaller barrels maybe supplied for applications falling outside the most commonly usedsizes. Accordingly, the system is very flexible. Sometimes, there is arequirement when preparing an injection for a first needle to draw thefluid from a vial and another to perform the injection using the samebarrel. Of course, the preferred embodiments of the present inventionare able to meet this requirement.

It is envisaged that blood collection (phlebotomy) may be used withembodiments of the invention, thus making “self-blunting” needlesunnecessary.

Due to the removability of the needles in preferred embodiments of theinvention, it is possible to keep barrels and needles apart before use.This gives flexibility and choice to e.g. the clinician who also hassecurity and cost-saving implications since stores of syringes arereadily targeted and robbed by drug users and medical personnel may alsobe targeted for theft. Accordingly, the ability to keep needlesseparately from barrels can reduce the risk of problems.

Another advantage is that preferred embodiments of the invention mayallow a plunger and safety needle to be fitted to a prefilled container,subject to dimensions, with a secure seal between the barrel and needlemounting. This is important since some prefilled syringes such as glasssyringes for Meningitis immunisation do not always have in the prior arta needle which sits tightly in the neck of the barrel and fluid leaksout. A further particular advantage is that devices such as hypodermicneedles in accordance with preferred embodiments of the presentinvention may be simple to use compared to other safety syringes and maybe priced at a level affordable to health services and workers in mostcountries since the cost may be similar to that of standard, i.e. basicreusable products.

The connector part 14 may be adapted such that in other embodiments,once the connector part is engaged with the retainer part, the fulllength of the legs 30 is located inside the connector part such thatthere is no passage for fluid past the connector part along the needleand the needle cannot therefore be used again to suck fluid into thebarrel.

Hubs 84 for needles of different sizes may be colour-coded to providehelpful information.

The syringe assembly 62 is preferably rubber-free, including the O ring78. Instead of using a push-on hub 84 as shown in FIGS. 4A to 4F for asyringe assembly 62 (it will be appreciated that the hub 84 snap-locksonto the front of the barrel in a conventional way), ahalf-turn/screw-lock may be implemented for the engagement of the hub 84with the barrel 64, this generally being considered the Americanconnection method, whereas the traditional conical snap connectionsystem is used more in Europe.

The barrel of the syringe assembly 62 may be made from various materialsincluding medical grade polypropylene. Alternatively, a clearpolycarbonate may be used. Other materials may be used. Once assembled,the medical device/syringe assembly may be sterilised, for example,using ethylene oxide or gamma rays or an electron beam method. Theplunger may be made from various materials including polyurethane orother suitable materials and the plunger may be coloured, for examplered or yellow or other suitable colours. The retainer part and connectorpart of the locking mechanism are preferably formed in plastics materialand the needle is most preferably steel, being rolled, welded, cut andpolished in a conventional way.

FIG. 10 shows a modification of the assembly shown in FIG. 4. Thesyringe barrel 100 in this embodiment has an eccentrically locatedforward neck portion 102, as shown in FIG. 10, which also shows fingertabs 104 of the assembly. As shown in FIG. 12, the needle 106 isretained by a retainer 12 the same as that shown in FIGS. 8 to 10 andthe plunger 108 has a connector part 104 located in an eccentricposition corresponding to the position of the neck 102 and needle 106,the connector part 14 being as shown and described with reference to theembodiments of FIGS. 1 to 4 and 7 to 9. The assembly in FIGS. 10 and 12includes an eccentrically domed hub 110. The plunger 108 has a stem 112with an X-shaped section. One arm 114 of the stem 112 runs in a groove116 defined by two grooved plates 118, only one of which is shown inFIG. 12, the plates preventing rotation of the plunger and stem. FIG. 11shows an alternative embodiment similar to the embodiment of FIG. 10,but the barrel 100 of the syringe assembly has a non-circular section,namely an elliptical section. In this embodiment, the groove and plates116,118 may be omitted. It will be appreciated that the side view of theFIG. 11 embodiment is shown in FIG. 12, as is the side view of the FIG.10 embodiment. In both of these embodiments, the needle 106 is retainedin place by lugs 46 on an internal recess of the syringe, and, oncefully depressed, the connector part 14 on the plunger 108 engages withthe retainer part 12, and the needle 106 is then retracted inside thesyringe assembly, on retraction of the plunger 108.

The use of a medical device such as a syringe assembly having aneccentric neck portion may be desirable in cases in which thecross-dimension or diameter of the assembly is relatively large. Theeccentric location of the neck portion may enable a user of the assemblyto place the assembly relatively close to or relatively parallel to abody surface of a patient, for example, for inserting a needle at ashallow angle into a patient.

In the syringe assemblies of FIG. 4 and FIGS. 10 to 12, an importantadvantage is that the retainer 12 and needle 22 may be compatible withvarious syringe plunger devices or other devices and/or that the neck ofthe syringe may be connected to various types of device such as a needlewith hub or a tube for pushing or sucking fluid along the tube. Thus,one type of locking mechanism/needle may be applicable to variousdevices, thus reducing costs. For example, the same locking mechanism,i.e. retainer part 12 and connector part 14 may be used in 1, 5, 10, 20ml or other sizes of hypodermic syringe assembly. Instead of using thebubble or dome-shaped hub 84 shown in FIGS. 4A to 4F and the eccentricbubble or dome-shaped hub shown in FIG. 12, a standard hub like the hub84′ may be employed.

Devices in accordance with the invention may have application in eitherhuman medical or veterinary fields and may even have application outsidemedical fields.

Various modifications may be made to the embodiments shown withoutdeparting from the scope of the invention as defined by the claims asinterpreted under Patent Law.

1. A locking mechanism for controlling engagement between parts movablerelative to one another in medical sharp devices, the mechanismcomprising: a retainer part for retaining a medical sharp, the retainerpart having a first formation which is engageable with a secondformation located on a body part of a medical sharp device and aconnector part which is movable relative to the body part to a positionin which the connector part and retainer part are in a mutually engagedconfiguration, wherein the connector part, during movement to theengaged configuration, is adapted to alter the relative engagementbetween the first and second formations to enable release of theretainer part from the body part, the retainer part including twoflexible legs, each leg having a said first formation located thereon,the connector part being adapted to flex the legs, on engagement withthe retainer part, to move the legs towards one another, the legs beingmutually joined at respective distal ends thereof before movement of theconnector part to the engaged configuration, the legs being arranged todisengage from the body part when moving toward one another.
 2. Alocking mechanism as claimed in claim 1 in which the first formation andsecond formation comprise a lug and a recess, each being formed on or inone of the retainer part and the body part.
 3. A locking mechanism asclaimed in claim 2 in which a pair of said lugs are provided on oppositesides of the retainer part and in which the recess comprises an internalannular recess in the body part.
 4. A locking mechanism as claimed inclaim 1 in which the legs form a diamond shape.
 5. A locking mechanismas claimed in claim 1 in which each leg has an inner surface and anouter surface, the outer surface being longer than the inner surface. 6.A locking mechanism as claimed in claim 5 in which the inner surface isrelatively flat and the outer surface is outwardly concave or relativelycurved compared to the inner surface.
 7. A locking mechanism as claimedin claim 1 in which the connector part includes a bore into which atleast part of the retainer part is insertable.
 8. A locking mechanism asclaimed in claim 7 in which the bore includes an annular ledge at anentrance thereto, and in which the retainer part includes at least oneconnector protrusion for engagement behind the annular ledge.
 9. Alocking mechanism as claimed in claim 8 in which two said connectorprotrusions are provided, the connector protrusions being adapted toengage the annular ledge asymmetrically.
 10. A locking mechanism asclaimed in claim 9 in which each connector protrusion has a chamferedsurface for riding over the annular ledge and an opposing step surfacefor engagement behind the ledge.
 11. A locking mechanism as claimed inclaim 1 in which the retainer part is adapted to retain a hypodermicneedle, the retainer part including an elongate bore passingtherethrough, the bore being engageable with a cylindrical outer surfaceof a needle.
 12. A locking mechanism as claimed in claim 11 in which theelongate bore includes internal ribs for sealingly gripping a needle.13. A medical device including a locking mechanism as claimed inclaim
 1. 14. A medical device as claimed in claim 13 which comprises ahypodermic needle device.
 15. A medical device as claimed in claim 14which comprises a butterfly.
 16. A medical device as claimed in claim 14which comprises a catheter.
 17. A medical device as claimed in claim 14which comprises a hypodermic syringe and in which the retainer part isadapted to retain a hypodermic needle of the device and the connectorpart is mounted on a plunger of the syringe.
 18. A medical device asclaimed in claim 17 in which the syringe includes a barrel, a conicalshoulder portion at a forward end of a main cylindrical part of thebarrel and a neck portion in front of the shoulder portion, the saidsecond formation of the locking mechanism being formed internally in theneck portion.
 19. A medical device as claimed in claim 18 in which theneck portion of the barrel includes a front end and a rear end, the rearend being adjacent a front end of the shoulder portion, the secondformation comprising an annular internal recess formed at the rear endof the neck portion.
 20. A medical device as claimed in claim 13 inwhich the retainer part is removably mounted on the body part of thedevice.
 21. A medical device as claimed in claim 20 in which theretainer part is removably mounted on the body part of the device, andwhich includes a hub part for releasably sealably retaining the retainerpart on the barrel of the syringe.
 22. A medical device as claimed inclaim 21 in which the hub includes a stop surface for preventing forwardmovement of the retainer part relative to the barrel.
 23. A lockingmechanism as claimed in claim 1 in which the distal ends of the legs arejoined together as a V-shaped end portion.
 24. A locking mechanism for amedical device comprising a retainer part for retaining medical sharpdevices, the retainer part including at least one connector portionthereof adapted for engagement against a body part of a medical sharpdevice, and a connector part, the connector part being adapted formovement to engage the connector portion for connection therewith,movement of the connector part once connected to the connector portioncausing movement of the retainer part, the connector portion comprisingtwo flexible legs, the connector part being adapted to flex the legs, onengagement with the connector portion, to move the legs towards oneanother, the legs being mutually joined at respective distal endsthereof before movement of the connector part to the engagedconfiguration, the legs being arranged to disengage from the body partwhen moving toward one another.
 25. A locking mechanism as claimed inclaim 24 in which the legs are joined together in a diamond shape.
 26. Alocking mechanism as claimed in claim 24 in which each said leg includesa formation adapted for engagement with a recess formed in the bodypart.
 27. A locking mechanism as claimed in claim 24 in which theconnector part includes a generally cylindrically bore, the bore beingadapted to receive each said leg on engagement of the connector parttherewith.
 28. A locking mechanism as claimed in claim 27 in which thebore includes an annular ledge at an entrance thereto and each said legincludes a connector projection adapted to ride over the lock past theledge on insertion to the bore.
 29. A medical device including a needleassembly as claimed in claim
 24. 30. A locking mechanism as claimed inclaim 24 in which the distal ends of the legs are joined together as aV-shaped end portion.
 31. A locking mechanism for controlling engagementbetween parts movable relative to one another in medical sharp devices,the mechanism comprising: a retainer part for retaining a medical sharp,the retainer part having a first formation which is engageable with asecond formation located on a body part of a medical sharp device and aconnector part which is movable relative to the body part to a positionin which the connector part and retainer part are in a mutually engagedconfiguration, wherein the connector part, during movement to theengaged configuration, is adapted to alter the relative engagementbetween the first and second formations to enable release of theretainer part from the body part, the retainer part including twoflexible legs, each leg having a said first formation located thereon,the connector part being adapted to flex the legs, on engagement withthe retainer part, to move the legs towards one another, the legs beingintegrally formed with the respective distal ends thereof being mutuallyjoined together, the legs being arranged to disengage from the body partwhen moving toward one another.
 32. A locking mechanism as claimed inclaim 31 in which the first formation and second formation comprise alug and a recess, each being formed on or in one of the retainer partand the body part.
 33. A locking mechanism as claimed in claim 32 inwhich a pair of said lugs are provided on opposite sides of the retainerpart and in which the recess comprises an internal annular recess in thebody part.
 34. A locking mechanism as claimed in claim 31 in which thelegs form a diamond shape.
 35. A locking mechanism as claimed in claim31 in which each leg has an inner surface and an outer surface, theouter surface being longer than the inner surface.
 36. A lockingmechanism as claimed in claim 35 in which the inner surface isrelatively flat and the outer surface is outwardly concave or relativelycurved compared to the inner surface.
 37. A locking mechanism as claimedin claim 31 in which the connector part includes a bore into which atleast part of the retainer part is insertable.
 38. A locking mechanismas claimed in claim 37 in which the bore includes an annular ledge at anentrance thereto, and in which the retainer part includes at least oneconnector protrusion for engagement behind the annular ledge.
 39. Alocking mechanism as claimed in claim 38 in which two said connectorprotrusions are provided, the connector protrusions being adapted toengage the annular ledge asymmetrically.
 40. A locking mechanism asclaimed in claim 39 in which each connector protrusion has a chamferedsurface for riding over the annular ledge and an opposing step surfacefor engagement behind the ledge.
 41. A locking mechanism as claimed inclaim 31 in which the retainer part is adapted to retain a hypodermicneedle, the retainer part including an elongate bore passingtherethrough, the bore being engageable with a cylindrical outer surfaceof a needle.
 42. A locking mechanism as claimed in claim 41 in which theelongate bore includes internal ribs for sealingly gripping a needle.43. A locking mechanism for a medical device comprising a retainer partfor retaining medical sharp devices, the retainer part including atleast one connector portion thereof adapted for engagement against abody part of a medical sharp device, and a connector part, the connectorpart being adapted for movement to engage the connector portion forconnection therewith, movement of the connector part once connected tothe connector portion causing movement of the retainer part, theconnector portion comprising two flexible legs, the connector part beingadapted to flex the legs, on engagement with the connector portion, tomove the legs towards one another, the legs being integrally formed withthe respective distal ends thereof being mutually joined together, thelegs being arranged to disengage from the body part when moving towardone another.
 44. A locking mechanism as claimed in claim 43 in which thelegs are joined together in a diamond shape.
 45. A locking mechanism asclaimed in claim 43 in which each said leg includes a formation adaptedfor engagement with a recess formed in the body part.
 46. A lockingmechanism as claimed in claim 43 in which the connector part includes agenerally cylindrically bore, the bore being adapted to receive eachsaid leg on engagement of the connector part therewith.
 47. A lockingmechanism as claimed in claim 46 in which the bore includes an annularledge at an entrance thereto and each said leg includes a connectorprojection adapted to ride over the lock past the ledge on insertion tothe bore.
 48. A medical device including a needle assembly as claimed inclaim
 43. 49. A medical device including a locking mechanism as claimedin claim
 43. 50. A medical device as claimed in claim 49 which comprisesa hypodermic needle device.
 51. A medical device as claimed in claim 50which comprises a butterfly.
 52. A medical device as claimed in claim 50which comprises a hypodermic syringe and in which the retainer part isadapted to retain a hypodermic needle of the device and the connectorpart is mounted on a plunger of the syringe.
 53. A medical device asclaimed in claim 52 in which the syringe includes a barrel, a conicalshoulder portion at a forward end of a main cylindrical part of thebarrel and a neck portion in front of the shoulder portion, the saidsecond formation of the locking mechanism being formed internally in theneck portion.
 54. A medical device as claimed in claim 53 in which theneck portion of the barrel includes a front end and a rear end, the rearend being adjacent a front end of the shoulder portion, the secondformation comprising an annular internal recess formed at the rear endof the neck portion.
 55. A medical device as claimed in claim 49 whichcomprises a catheter.
 56. A medical device as claimed in claim 49 inwhich the retainer part is removably mounted on the body part of thedevice.
 57. A medical device as claimed in claim 56 in which theretainer part is removably mounted on the body part of the device, andwhich includes a hub part for releasably sealably retaining the retainerpart on the barrel of the syringe.
 58. A medical device as claimed inclaim 57 in which the hub includes a stop surface for preventing forwardmovement of the retainer part relative to the barrel.
 59. A lockingmechanism as claimed in claim 43 in which the distal ends of the legsare joined together as a V-shaped end portion.
 60. A locking mechanismas claimed in claim 43 in which the distal ends of the legs are joinedtogether as a V-shaped end portion.